Iona Industries acquired a packaging machine used in its factory operations for $160,000. The machine was originally estimated to have a useful life of 5 years and a salvage value of $40,000. Iona uses the straight-line method of depreciation. Iona sold the machine on the last day of the third year for cash equal to its book value. Depreciation had been recorded through the date of sale. a. What was the net book value of the machine on the sale date?